If the OBR forecasts a triple-dip recession and a higher deficit this year, the Chancellor's failure will be clearer than ever.

After a notable absence of Budget leaks, last night brought a slew of pre-briefed announcements. Today's Sunreveals that Osborne will scrap next month's 6p rise on a pint of beer and abolish the beer duty escalator, while the Guardian reports that he will announce an increase in the personal allowance to £10,000, a year ahead of schedule, and either delay or cancel the fuel duty rise. After last year's disastrous decision to abolish the 50p tax rate, brilliantly framed by Labour as the "millionaires' tax cut", all three measures are intended to signal that the Chancellor's priority is now reducing the cost of living for those famed "hardworking families". Osborne has wisely resisted calls from the Thatcherite right to abolish capital gains tax or slash corporation tax to an Irish-style 11 per cent - measures that would largely benefit the well-off.

But what we won't get until the Chancellor stands up at 12:30pm are the Office for Budget Responsibility's updated forecasts for growth, borrowing and employment - and here's where the pain could lie for Osborne.

For the fifth time since it was established, the OBR is expected to downgrade its growth forecasts. Growth in 2013, which was predicted to be 1.2 per cent in the Autumn Statement, is now likely to be only half that amount. But the most important figure, for the Chancellor's immediate political prospects, will be that for the first quarter of this year. It is this number that will determine whether Britain has suffered an unprecedented "triple-dip recession". We won't get the first estimate from the Office for National Statistics until 26 April but a negative forecast from the OBR would make it far harder for Osborne to claim that "we're on the right track". A third recession in four years is the Chancellor's first nightmare.

The second is a higher deficit. Until now, even as growth has disappeared, the Chancellor has been able to boast that borrowing "is falling" and "will continue to fall each and every year". But today, for the first time since he entered the Treasury, Osborne will almost certainly be forced to announce that the deficit is forecast to be higher this year than last. Even with the addition of £2.3bn from the auction of the 4G mobile spectrum, borrowing is currently £3bn higher than in 2012. As the OBR noted last month, "to meet our autumn forecast would now require much stronger growth in tax receipts in the last two months of the year than we have seen since December, or much lower-than-forecast expenditure by central or local government". Expect Robert Chote and his fellow number-crunchers to announce that fate has failed to favour the Chancellor.

The combination of a shrinking economy and a rising deficit will add force to Labour's charge that austerity is "hurting but not working". With Osborne also expected to announce that the national debt won't begin to fall as a proportion of GDP until 2017-18 (two years behind schedule), even some Tory MPs are beginning to ask what all the pain has been for.

To all of this, the Chancellor's inevitable riposte to Labour will be "but you would borrow even more!" One of the key tests for Ed Miliband (who, as leader of the opposition, will reply to Osborne, rather than Ed Balls) will be how or whether he seeks to rebut this charge.